Constant force balance spring #12

Home Owner from honolulu

Aug 4, 2018 9:35 pm

Don't know if you can help me, I'm looking for replacement constant force balance springs to replace the OEM springs used in my window wall which have ~ a 3 year life before failure. They are installed in a double hung, double glazed window assembly with each sash being 32" high and 29" wide. Currently using a #12 balance spring. The OEM assembly measures 4 5/8" long, 1 1/4" wide with two coils of ~1/2" metal springs.

Thank you in advance for looking over my request...Greg

2 user uploaded images

9 Replies

Paul from SWISCO

Aug 8, 2018 10:49 am

Your coil spring system looks very close to our S140-12. Take a look and see if this is the correct replacement for you.

Paul from SWISCO

Aug 8, 2018 11:33 am

The typical life span of a coil balance spring system is usually 5-10 years depending on the usage of the window. It's best to stick with the same type of system you have before. If you believe it is incorrect, you can always weigh the sash of your window to make sure the spring strength is accurate. You don't want to go too light or too heavy on your spring system because then the window will not function properly.

Home Owner from honolulu

Aug 8, 2018 12:04 pm

Thank you...these look like an exact fit.

Do you have any data as to the expected life span, or cycles that I could expect from the S140-12?

Does the spring weight determine the life span or just the lift/hold power..like would an S140-10 be better?

Home Owner from honolulu

Aug 8, 2018 2:32 pm

Thanks Paul...I'll weigh the window sash and then decide what makes sense. We live in Hawaii, so we open and close the windows pretty much every day..My estimate is once per day for 300 days per year...or about 1000 cycles ~ 3 years to failure where the top spring of the dual coil cracks and breaks.

I'm trying to determine if it is a "normal" expectation, a manufacturer issue via design or tempering, a weight impact..balance springs to weak or strong...etc...

Home Owner from honolulu

Aug 12, 2018 11:24 am

Hello Paul,

I've weighed the window sash...21.5 lbs each. Does SWISCO produce a S-140-11 in a single spring or is the S-140-12 dual spring my only option?

Once again, thank you for your help...Greg

Tom from SWISCO

Aug 13, 2018 12:42 pm

I'm afraid we don't have a single spring S140-11, but I see no reason why our dual spring S140-11 won't work. If your sash is 21.5 pounds, this may be your best option, but to be honest our S140-12 could still work. If that's what you had before, and if it worked fine for years, then I see no reason to change.

Home Owner from honolulu

Aug 13, 2018 8:24 pm

Thanks again...Ok..I'll order 4 to try out. Your recommendation please...the S140-11 or the S140-12. I'm looking for the most trouble free, with the longest cycle life..since I'd guess either one would hold the window in place..Greg

Tom from SWISCO

Aug 14, 2018 12:19 pm

Yep, pretty much. I don't think either would be stronger or last longer than the other. That's why we usually recommend to stick with what you have.